Alternating current generators, in particular of high power (several hundred megawatts (MW)), are connected to electricity distribution networks the demand of which varies greatly.
These generators are subjected to varied disturbances of very different kind and magnitude: short circuits, voltage drops, load variation, load shedding, etc. In all cases, and throughout their operating range, performance as close as possible to the optimum is expected. Closed loops must also have sufficient stability margins.
The regulation methods used at present, in particular for high-power alternators in nuclear power stations, are based on the so-called four-loop regulator principle, the feedback (FBK) loops of which are used to maintain the output values as close as possible to a reference value, notably by controlling a certain number of controllable parameters.
These methods based on analogue technologies are highly sensitive to measurement errors and are even relatively ineffective in assuring the stability of closed loops over a wide range. In particular, these closed loop methods generate oscillations that are difficult to damp out and often poorly damped.
These regulation methods and the regulators applying them more particularly fail to meet the technical specifications of electricity suppliers relating to exciter and voltage adjustment equipment of high-power alternators in nuclear power stations over the whole of the range of use.